Superheated steam is steam obtained by further heating steam (saturated vapor) at 100° C. at atmospheric pressure. Superheated steam has unique advantages when used for such purposes as heating, burning, roasting, carbonization, or sterilization, causing, manufacturers in various fields, including foods, health care, and environment-related apparatuses, to pay attention to it. If superheated steam contacts an object whose temperature is 100° C. or lower, it condenses into water and generates a great deal of heat that is transferred to the object. Also, superheated steam can dry and burn objects if its temperature is over 100° C., because it is in a gaseous state if its temperature is over 100° C. Moreover, superheated steam has high heat capacity per unit volume compared to high-temperature air or exhaust gas, so a small amount of superheated steam can dry or burn an object in a short time.
A superheated-steam oven cooks foodstuffs by directly blowing steam at 100° C. or higher to the foodstuffs. The steam contacts and surrounds the foodstuffs that are to be cooked, so as to reduce the time needed to heat them. In the conventional art, as disclosed in Japanese Unexamined Patent Application No. 2003-262338, a superheated-steam spray nozzle and a superheated-steam generator are installed separately, and the superheated-steam generator is connected to the spray nozzle by a pipe so as to send superheated steam through the pipe from the generator to the nozzle.    Patent document 1: Japanese Unexamined Patent Application No. 2003-262338